7. Billy was in a car accident and sustained head injuries. Some of the injury occurred in areas of the brain that use glutamate. The damage caused the glutamate, the chief excitatory neurotransmitter in the brain, to spill out onto adjoining brain tissue. To their amazement, the doctors discovered that these areas of tissue died when exposed to the glutamate.

The doctors concluded that the neurons in these regions were stimulated to death. This piece of research is best described as a(n) .

a. experiment

b. correlational study

c. case study

d. naturalistic observation